In the life science field, electrophoresis is one of the significantly useful separating and analyzing techniques. It is used for separating biopolymers, such as protein, DNA, RNA, and the like. It is also possible to separate cells. In addition to a typical electrophoresis method with use of gel, a Capillary electrophoresis method with use of buffer solutions containing a polymer and a Free Flow Electrophoresis method carried out in free solution have been performed.
As a technique to improve electrophoresis, Japanese Utility Model Publication, Jitsukaihei, No. 5-4004 (date of publication: Jan. 22, 1999) discloses that disruption in electrophoresis pattern due to uneven electrophoresis field is prevented by providing a wire-shaped electric conductor in an electrophoresis chamber.
Also, Japanese Utility Model Publication, Jitsukaihei, No. 5-4003 (date of publication: Jan. 22, 1993) discloses that provision of an intermediate electrode in an electrophoresis chamber actively controls distributions of electric fields and electric potentials in the electrophoresis chamber.
As a result of study, however, the present inventors identified that the electrophoresis devices having an electric conductor in an electrophoresis chamber, such as the electrophoresis devices in the above documents have a problem of decline in electrophoresis speed.
Also, in Proteome analysis, it is necessary to simplify a series of procedures including first electrophoresis, second electrophoresis, and transferring a sample to a membrane, which are carried out continuously.
Japanese Publication for Unexamined Patent Application, Tokukai, No. 2007-64848 (date of publication: Mar. 15, 2007) discloses an electrophoresis device for automating the first electrophoresis and the second electrophoresis.
Japanese Publication for Unexamined Patent Application, Tokukai, No. 2000-28578 (date of publication: Jan. 28, 2000) discloses a device for electrophoresis and transfer.
However, a device disclosed in Japanese Publication for Unexamined Patent Application, Tokukai, No. 2000-28578 (date of publication: Jan. 28, 2000) still requires a complicated and skillful procedure such as a removal of gel after an electrophoresis.
Japanese Publication for Unexamined Patent Application, Tokukai, No. 2006-71494 (date of publication: Mar. 16, 2006) proposes an easy-operation device for electrophoresis and transfer which does not require the removal of gel.
However, a practical and easy-operation device for electrophoresis and transfer is not yet in existence.
According to the study of the present inventors, electrophoresis devices merely having an electrode for transfer in the middle of the electrophoresis path, such as a device disclosed in Japanese Publication for Unexamined Patent Application, Tokukai, No. 2006-71494 (date of publication: Mar. 16, 2006), have a difficulty in performing an electrophoresis. Specifically, the electrophoresis device with the above structure failed to apply a voltage and migrate a sample in the process of electrophoresis.
Further, in analyzing a result of an electrophoresis, it is widely performed that a sample in gel are transferred to a membrane and carrying out an antigen antibody reaction on the membrane.
As a method for transferring a sample in gel to a membrane, there are several methods such as a way of using capillary action and a way of using a voltage difference. (Referring to a book “DENKIEIDOU NARUHODO Q&A” (“Electrophoresis Q & A”) P. 161 to 163, written by Michihiro Ofuji, published by Yodosha in 2005)
However, the present inventors identified that transfer efficiency was declined in some samples in transferring them in gel to a membrane under a conventional transfer method.
A first feature of an example embodiment presented herein is to prevent decline in electrophoresis speed in an electrophoresis device including an electric conductor in an electrophoresis chamber.
As a result of diligent studies, the present inventors identified that a cause of the decline in electrophoresis speed was in a conventionally unidentified phenomenon. The phenomenon is that air bubbles generated at an electric conductor in an electrophoresis chamber detach gel from the electric conductor, and a buffer solution goes into the gap between the gel and the electric conductor, thereby attaining inhibition of a buffer action.
Then, the present inventors studied further and found that the air bubbles are not generated when an electric potential difference between adjacent electric conductors is under a certain voltage, and accomplished the invention based on the finding.
Namely, a device for electrophoresis of the present embodiment is configured to separate separation target components in a medium in which a plurality of electric conductors are provided in contact with the medium, including voltage applying means configured to apply a voltage to the medium, so that a potential difference between adjacent electric conductors is more than 0V but not more than 0.3V.
With this structure, the voltage applying means applies a voltage so that a potential difference between adjacent electric conductors is more than 0V but not more than 0.3V. If the potential difference between adjacent electric conductors is not more than 0.3, no air bubbles generate as shown in embodiment examples described later. Therefore, this structure is capable of suppressing decline in electrophoresis speed due to the emergence of air bubbles.
In the electrophoresis device with this structure, the voltage applying means may apply the voltage to each of the electric conductors.
According to this structure, the voltage applying means may apply a potential to each of the electric conductors directly so that it is easy to set a potential difference between adjacent electric conductors more than 0V but not more than 0.3V.
It is preferable that the device for electrophoresis has 250 or more electric conductors.
According to this structure, it is easy to control a potential difference between adjacent electric conductors not more than 0.3V by only applying a voltage which is in normal range voltage for electrophoresis (from 50V to 500V) to gel.
It is preferable that the electric conductor is line-shaped in the device for electrophoresis.
With this structure, it is easy to control a potential difference between adjacent electric conductors not more than 0.3V with use of narrow line-shaped electric conductors which allow arranging a number of electric conductors.
It is preferable that the line-shaped electric conductors are arranged in parallel one another and extend in an orthogonal direction to the direction in which the voltage applying means applies a voltage to the medium.
According to this structure, the line-shaped electric conductors are arranged in parallel one another and extend in an orthogonal direction to the direction in which the voltage applying means applies a voltage to the medium. Therefore, the electric conductors do not affect a potential gradient toward the first direction, thereby making it possible to separate the separation target components in the medium favorably.
It is preferable that the line-shaped electric conductor is not more than 10 μm in thickness in the device for electrophoresis.
With this structure, it is easy to control a potential difference between adjacent electric conductors not more than 0.3V with use of the narrow line-shaped electric conductors which allow arranging a number of electric conductors even in a small sized device.
It is preferable that the distance between adjacent electric conductors is not more than 100 μm in the device for electrophoresis.
With this structure, it is easy to control a potential difference between adjacent electric conductors not more than 0.3V because of the narrow space between the electric conductors, which allows arranging a number of electric conductors even in a small sized device.
It is preferable in the device for electrophoresis that the electric conductor is made of metal selected from the group consisting of platinum, zinc, and copper.
This structure allows performing a method for electrophoresis of the present embodiment repeatedly because the electric conductor is less likely to be deteriorated.
The device for electrophoresis may be an isoelectric electrophoresis device.
This structure allows forming a uniform pH gradient in a medium in an isoelectric electrophoresis device.
A method for the electrophoresis of the present embodiment is a method for separating separation target components in a medium in which a plurality of electric conductors are provided in contact with the medium, including applying a voltage to the medium so that a potential difference between adjacent electric conductors is more than 0V but not more than 0.3V.
With this arrangement, in the process of applying voltage, a voltage is applied so that a potential difference between adjacent electric conductors is more than 0V but not more than 0.3V. When the voltage between the adjacent electric conductors is not more than 0.3V, air bubbles do not generate. Therefore, this arrangement allows preventing the decline in electrophoresis speed due to the generation of air bubbles.
A second feature of the present embodiment is to provide a practical and easy-to-use device for electrophoresis and transfer, a chip for electrophoresis and transfer, and a method for electrophoresis and transfer.
As a result of diligent studies, the present inventors found that it is possible to perform an electrophoresis with ease, even though an electrode for transfer is provided in the middle of the electrophoresis path, by using the electrode having a plurality of electrode regions being insulated one another and arranged in a direction of electrophoresis path.
Namely, a device for electrophoresis and transfer of the present embodiment includes first voltage applying means configured to apply a voltage with respect to a specific direction in the first medium having separation target components, and second voltage applying means configured to apply a voltage to the first medium toward a direction of a second medium being in contact with the first medium, the second voltage applying means including a first electrode having a plurality of electrode regions being insulted one another and arranged in the specific direction.
According to this structure, the device for electrophoresis and transfer of the present embodiment can separate separation target components in the first medium, and then transfer the separated separation target components to the second medium. For example, it is very useful to use the device for electrophoresis and transfer which can perform both an electrophoresis and a blotting easily in an analysis of biopolymer.
In a conventional device for electrophoresis and transfer, however, the electrode, which is provided in the second voltage applying means for transferring separation target components in a first medium to a second medium, hampers the separation of the separation target components in the first medium. Therefore, the conventional device was not useful.
However, with this structure, the second voltage applying means includes the first electrode having a plurality of electrode regions being insulated one another and arranged in the specific direction. Since the electrode regions in the first electrode are insulated one another and arranged in the specific direction, the separation of the separation target components in the first medium is not hampered. Namely, with this structure, it is possible to perform an electrophoresis and a transfer practically and easily.
It is preferable that the electrode region is line-shaped in the device for electrophoresis and transfer.
According to this structure, each of the electrode regions is line-shaped which enables to fill up the surface easily when they are arranged in the specific direction. This allows transferring the separation target components in the first medium to the second medium efficiently.
It is preferable that the plurality of electrode regions are arranged in parallel one another and extend in an orthogonal direction to the specific direction in the device for electrophoresis and transfer.
The line-shaped electrode regions arranged in parallel one another and extending in an orthogonal direction to the specific direction do not affect the voltage applied to the specific direction. This allows separating separation target components in the first medium favorably.
It is more preferable that the device for electrophoresis and transfer further includes wire connection means configured to switch the first electrode between connection and disconnection.
With this structure, it is possible to control a potential of the first electrode easily because the wire connection means is capable of switching the first electrode between connection and disconnection.
The second voltage applying means may further include a detachable second electrode in the device for electrophoresis and transfer.
According to this structure, the second voltage applying means has a detachable second electrode as well as the first electrode. This allows transferring the separation target components in the first medium to the second medium with ease without affecting the separation of separation target components in the first medium.
The device for electrophoresis and transfer may include a detachable holder configured to hold the second electrode and the second medium.
According to this structure, the second medium is easy to be used for further analysis since the second medium is detachable.
The second voltage applying means may further include a second electrode having a plurality of electrode regions being insulated one another and arranged in the specific direction in the device for electrophoresis and transfer.
According to this structure, the electrode regions in the second electrode do not hamper the separation of the separation target components in the first medium because the electrode regions are insulated one another and are arranged in the specific direction in which the separation target components in the first medium are separated. Therefore, it is possible to transfer the separation target components in the first medium to the second medium with ease without affecting the separation of separation target components in the first medium.
A chip for electrophoresis and transfer of the present embodiment includes a separation section configured to place a first medium having separation target components, and a second medium in contact with the first medium, a first buffer solution chamber and a second buffer solution chamber sandwiching the separation section, and a first electrode being provided on the separation section, and having a plurality of electrode regions being insulated one another and arranged in the specific direction specified by the first and the second buffer solution chambers.
According to this structure, it is possible to separate the separation target components in the first medium toward the specific direction by applying a voltage to the first medium provided on the separation section via the electrodes arranged in the first and second buffer solution chambers. At this time, the first electrode, which is provided on the separation section, has the electric regions being insulated one another and arranged in the above direction. This allows not affecting to the separation of the separation target components in the first medium.
The device realizes both electrophoresis and transfer because the first electrode allows applying a voltage to the separated separation target components easily, in a direction from the first medium toward the second medium.
A method for electrophoresis and transfer of the present embodiment includes (a) applying a voltage to the first medium having separation target components in the specific direction, and (b) applying a voltage to the first medium toward a direction of the second medium being in contact with the first medium, following the step (a), wherein in the step (b), the voltage is applied with use of the first electrode including a plurality of electrode regions being insulated one another and arranged in the specific direction.
With this arrangement, it is possible to perform electrophoresis and transfer favorably because the first electrode which is used in the second voltage applying process do not adversely affect the separation of the separation target components in the first medium in the first voltage applying process.
A third object of the present embodiment is made in view of the foregoing problem and is for providing a device for transfer preventing decline in transfer efficiency.
As a result of diligent sturdy, the inventors of the present embodiment found that there is a suitable transfer voltage depending on a molecular weight of a sample to be transferred and also found that it is possible to prevent decline in transfer efficiency by adjusting an applied voltage to the medium including the sample depending on positions. The present embodiment is accomplished based on the finding.
Namely, a device for transfer of the present embodiment is configured to transfer target components in the first medium to the second medium, including voltage applying means configured to apply a voltage to the first medium, the voltage applying means applying the voltage to the first medium in such a manner that a certain position and another position in the first medium are provided different voltages or different voltage durations.
With this structure, the transfer target components in the first medium such as agarose gel are transferred to the second medium such as a membrane by applying a voltage to the first medium. The voltage applied to the first medium varies depending on positions in the first medium. This allows applying a suitable voltage depending on a molecular weight of each of the transfer target components in the first medium, for example, SDS-PAGE separated polyacrylamide gel including transfer target components whose molecular weights differ in position in the gel.
According to the findings of the present inventors, there is a suitable voltage for transfer depending on a molecular weight of a transfer target component. In other words, the transfer efficiency declines when a voltage far from the suitable voltage is applied to the transfer target component. This structure allows applying a suitable voltage depending on the molecular weight of each of the transfer target components and preventing decline in transfer efficiency.
As described later, it is possible to obtain the same effect by adjusting a voltage duration applied to the transfer target components instead of adjusting an applied voltage to the transfer target components.
It is preferable that the voltage applying means increases the voltage stepwise or gradually toward the specific direction specified by the first medium in the device for transfer.
According to this structure, the voltage applied to the first medium increases toward the specific direction specified by the first medium. Accordingly, it is possible to apply a suitable voltage depending on the molecular weight of each of the transfer target components in the first medium such as polyacrylamide gel separated by SDS-PAGE including transfer target components in which the distribution of the molecular weight increases in one way.
The voltage applying means may increase an applied voltage duration stepwise or gradually toward the specific direction specified by the first medium in the device for transfer.
As described above, it is possible to obtain the same effect by adjusting a voltage duration applied to transfer target components instead of adjusting an applied voltage to transfer target components.
It is preferable that the voltage applying means includes the first electrode and the second electrode, each of which is divided into a plurality of electrode regions being insulated one another in the device for transfer.
According to this structure, each of the first and the second electrodes includes a plurality of electrode regions being insulated one another. Therefore, it is possible to provide a different potential to each of the electrode regions or a different potential duration to each of the electrode regions with ease.
It is preferable that the voltage applying means includes the first electrode and the second electrode, each of which is divided into a plurality of electrode regions arranged in the specific direction in the device for transfer.
According to this structure, each of the first and the second electrodes is divided into a plurality of electrode regions being insulated one another and arranged in the specific direction. Therefore, it is possible to increase an applied voltage or a voltage duration applied to the first medium toward the specific direction with ease.
It is preferable that each divisional shape of the electrode regions of the first electrode and each divisional shape of the electrode regions of the second electrode are substantially equal in the device for transfer.
According to this structure, it is possible to apply a voltage to the first medium accurately because the divisional shape of the electrode regions of the first electrode and the second electrode are substantially equal. Namely, an electrode region of the first electrode and a corresponding electrode region of the second electrode have a substantially equal shape. Therefore, an electric field applied by a potential difference between the first and the second electrode regions is easily predictable because the electric field is based on the shape of both electrode regions.
It is preferable that the electrode region is line-shaped in the device for transfer.
According to this structure, it is possible to generate a fine potential difference because each of the electrode regions is line-shaped.
It is preferable that the line-shaped electrode regions are arranged in parallel one another and extend in an orthogonal direction to the specific direction in the device for transfer.
This structure allows dividing a potential finely toward the specific direction.
The voltage applying means may apply the voltage to each of the electrode regions in the device for transfer.
This structure allows the voltage applying means to apply a potential to the electrode regions directly. Therefore, it is possible to adjust an applied voltage in accordance with the molecular weight of the transfer target components with ease.
In the device for transfer, the voltage applying means includes at least one power supply, and a plurality of conductive paths connecting the power supply and each of the electrode regions conductively, and the conductive paths may have at least two kinds of resistance values.
According to this structure, the conductive paths conductively connecting the power supply and each of the electrode regions have two or more kinds of resistance values. This allows applying two or more kinds of potentials to each of the electrode regions depending on the molecular weight of the transfer target components.
In the device for transfer, the voltage applying means may alter a potential duration applied to each of the electrode regions.
According to this structure, it is possible to apply a voltage for a suitable time period to the transfer target components depending on a molecular weight of each component because the voltage applying means controls a potential duration applied to the electrode regions.
In the device for transfer, the voltage applying means includes a power supply and a mobile electric conductive section conductively connecting the power supply and the plurality of conductive regions, and the mobile electric conductive section may alter duration of potential application to each of the electrode regions by its movement.
This structure allows the voltage applying means to control a potential duration applied to each of the electrode regions with ease.
The mobile electric conductive section may be bar-shaped in the device for transfer.
This structure allows the potential control means to control a potential duration applied to each of the electrode regions with ease.
In the device for transfer of the present embodiment, the voltage applying means applies the voltage to the first medium via an electric resistance layer, and a certain position and another position on the electric resistance layer may have different resistance values.
According to this structure, the voltage applying means applies a voltage to the first medium via the electric resistance layer and the electric resistance layer have various resistance values depending on positions. This allows the voltage applying means to apply different voltages to the first medium by positions with ease.
It is preferable that the voltage applying means applies a voltage to the first medium via the electric resistance layer in which a resistance value decreases stepwise or gradually to the specific direction specified by the first medium.
According to this structure, since the electric resistance layer has a stepwise or gradually decreasing resistance value to the specific direction specified by the first medium, the voltage applying means is able to increase an applied voltage stepwise or gradually to the first medium to the specific direction with ease.
It is preferable that the device for transfer further includes cooling means for cooling the voltage applying means.
According to this structure, the cooling means radiates heat in the voltage applying means and maintains optimum temperatures for the first and the second mediums, thereby making it possible to prevent affecting both mediums and the transfer target components qualitatively.
A method for transfer of the present embodiment is a method for transferring transfer target components in a first medium to a second medium including applying a voltage to the first medium, in such a manner that a certain position and another position in the first medium are provided different voltages or different potential durations.
According to this structure, it is possible to prevent decline in transfer efficiency by applying a suitable voltage depending on a molecular weight of each of the transfer target components same as the device for transfer of the present embodiment.
Additional features, and strengths of the present embodiment will be made clear by the description below. Further, the advantages of the present embodiment will be evident from the following explanation with reference to the drawings.